Apparatus including an orbiting-mass sonic oscillator for slip-forming concrete



p 23, 1969 A. G. BODINE. JR 3,

APPARATUS INCLUDING AN ORBITING-MASS SONIC OSCILLATOR FOR SLIP-FORMING CONCRETE Original Filed May 10, 1965 2 Sheets-Sheet 1 fi 3 L..n

INVENTOR ALBERT G. BODINE. JR.

BY SOKOLSKI Bu WOHLGEMUTH ATTORNEYS Sept. 23, 1969 A. e. BODINE. JR 3,468,001

APPARATUS INCLUDING AN ORBITING-MASS SONIC OSCILLATOR FOR SLIP-FORMING CONCRETE Original Filed May 10. 1965 2 Sheets-Sheet 2 lNVENTOR Bf ALBERT G. WDINEJR.

SOKOLSKI 8 WOHLGEMUTH BWCRNEY United States Patent US. C]. 25-41 4 Claims ABSTRACT OF THE DISCLOSURE The mold used for slip-forming concrete is resonantly vibrated as part of a resonant elastic vibration system as the concrete casting is being formed, thereby lowering the friction at the interface between the casting and the mold and improving the characteristics of the casting.

This application is a division of my application Ser. No. 454,335 filed May 10, 1965, now abandoned.

This invention relates to the slip-forming of concrete and more particularly to apparatus in which sonic energy is utilized to facilitate such forming.

In the slip-forming of concrete, a mold is generally utilized to form concrete aggregate to a desired shape and as the aggregate starts to set, the mold is moved along, permitting such aggregate to slip therefrom by gravity feed. In this manner, a continuous member having the cross-sectional configuration of the mold, such as a column or a slab, can be cast. Slip-form technique is used extensively in the construction of buildings, highways and the like.

It has been found in slip-forming techniques of the prior art that the surfaces of the concrete aggregate tend to adhere to the walls of the mold which results in tearing of the surfaces of the end product. In order to minimize such adhesion, a relatively wet aggregate must be used which presents problems of slump and sagging in the formation of the end product. The use of a wetter mix also makes for a longer setting time. Further, it is often difiicult to mix and wet the aggregate as completely as to be desired.

The apparatus of this invention overcomes the aforementioned shortcomings of the prior art by providing means for reasonantly vibrating the slip-forming mold as the casting is being made. Thus, high-level sonic energy is provided at the interface between the mold and the casting, thereby minimizing the friction therebetween. Further, the aggregate is sonically activated to improve the wetting and mixing thereof and to speed up the setting of the aggregate.

In carrying out the technique of the invention, a mold member is used having an upper open end for receiving concrete aggregate to be cast, and a lower open end for exiting the concrete as it sets. Means are provided to move the mold to effect the exiting of the formed concrete therefrom. An orbiting-mass oscillator is connected to the mold. The oscillator is driven at a frequency such as to cause resonant elastic vibration of the mold such as to provide low friction at the interface between the mold and concrete and to sonically activate the aggregate to improve the setting thereof.

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It is therefore an object of this invention to facilitate the slip-forming of concrete.

It is another object of this invention to provide apparatus for slip-forming concrete which produces a casting having improved structural characteristics.

It is still another object of this invention to provide means for reducing the setting time in the slip-forming of concrete.

Other objects of this invention will become apparent from the following description taken in connection with the accompanying drawings, of which:

FIG. 1 is an elevation view illustrating a first embodiment of the device of the invention;

FIG. 2 is a perspective view of a second embodiment of the device of the invention; and

FIG. 3 is a perspective view illustrating the oscillator and resonant bar utilized in the embodiment of FIG. 2.

In order to facilitate the comprehension of the operation of the device of the invention, it is helpful to make an analogy between an electrical resonant circuit and a mechanical resonant circuit. This type of an analogy is well known to those skilled in the art and is described, for example, in Chapter 2 of Sonics by Hueter and Bolt, published in 1955 by John Wiley and Sons. In making such an analogy, force F is equated with electrical voltage E, velocity of vibration u is equated with electrical current i, mechanical compliance C is equated With electrical capacitance C mass M is equated with electrical inductance L, mechanical resistance (such as friction) R is equated with electrical resistance R, mechanical impedance Z is equated with electrical impedance Z Thus, it can be shown that if a member is elastically vibrated by a sinusoidal force F sin wt, 0: being equal to 21r times the frequency of vibration, that 1 F sin wt Z -R (00M cm) u Where wM is equal to l/wC a resonant condition exists, and the effective mechanical impedance Z is equal to the mechanical resistance R the reactive impedance components wM and l/wC cancelling each other out. Under such a resonant condition, velocity of vibration u is at a maximum, elfective power factor is unity, and energy is most efiiciently delivered to the object being vibrated. It is this high-efficiency resonant condition in the elastic system that is preferably utilized in the methods and devices of this invention to achieve the desired end results.

It is to be noted by reference to Equation 1 that velocity of vibration u is highest where impedance Z is lowest, and vice versa. Therefore, a high-impedance load will tend to vibrate at relatively low velocity, and vice versa. Thus, at an interface between highand low-impedance elements, a high relative movement results by virtue of such impedance mismatch which, as in the equivalent electrical circuit, results in a high reflected wave. Such an impedance mismatch condition between a mold and the material being formed therein can be utilized to free the material from such mold and effectively provide low friction between the two.

Just as the sharpness of resonance of an electrical circuit is defined as the Q thereof, and is indicative of the ratio of energy stored to the energy used in each cycle, so also the Q of the mechanical resonant circuit has the same significance and is equal to the ratio between wM and R Thus, high efliciency and considerable cyclic motion can be achieved by designing the mechanical resonant circuit for high Q.

Of particular significance in the implementation of the devices of this invention is the high acceleration of the components of the elastic resonant system that can be achieved at sonic frequencies. The acceleration of a vibrating mass is a function of the square of the frequency of the drive signal times the amplitude of vibration. This can be shown as follows:

The instantaneous displacement y of a sinusoidally vibrating mass can be represented by the following equation:

y=Y cos wt (2) where Y is the maximum displacement in the vibration cycle and w is equal to 21f, 1 being the frequency of vibration.

The acceleration a of the mass can be obtained by differentiating Equation 2 twice, as follows:

The acceleration a thus is a function of Y times (21rf) At resonance, Y is at a maximum and thus even at moderately high sonic frequencies, very high accelerations are achieved.

In considering Equation 1, several factors should be kept in mind. Firstly, this equation represents the total elfective resistance, mass, and compliance in a mechanical circuit, and these parameters are generally distributed throughout the system rather than being lumped in any one component or portion thereof. Secondly, the vibrating system often includes not only the mold but surrounding components. Thus, it may be desirable to purposely add members exhibiting predominantly compliance C or mass M characteristics to balance out one or the other of these parameters to make for a resonant system. Thirdly, an orbiting-mass oscillator is utilized with the device of the invention that automatically adjusts its out put frequency to maintain resonance with changes in the characteristics of the load. Thus, where we are dealing with a fluid material which solidifies in the process involved and thereby changes its characteristics, the system automatically is maintained at optimum resonant operation by virtue of the lock-in characteristics of applicants unique orbiting-mass oscillators. With the basic considerations in mind, let us now turn to the specific embodiments of the device of the invention.

Referring now to FIG. 1, a first embodiment of the device of the invention in the slip-forming of concrete columns is illustrated. Concrete 101 is poured from chute 103 into funnel-shaped forming mold 105. As the concrete sets, mold 105 is raised upwardly along with chute 103. Solid concrete column 107 is thus formed. During the process sonic energy is applied to mold 105 from resonant bar 108, which is attached thereto. Bar 108 is resonantly excited by orbiting-mass oscillator 110, which is attached thereto to produce standing waves 112. Funnelshaped mold 105 becomes part of a resonantly vibrating system including bar 108. Oscillator 110 is preferably an orbiting-mass oscillator driven by a motor 115, such as for example that described in connection with FIGS. 9-12 of my Patent No. 3,299,722 issued Jan. 24, 1967. This type of oscillator is capable of providing relatively high power output and therefore is preferable in applications such as this involving heavy load requirements. This orbiting-mass oscillator will .automatically adjust its frequency with changes in the characteristics: of the material being cast.

To attain optimum results, it is desirable to start the sonic oscillator with the first pouring of concrete, before the raising of mold 105 is initiated, and to continue such vibration for a time after the mold is stopped in its final topmost position.

In view of the impedance mismatch at the interfaces .4 between mold and the material being cast, considerable sonic activity occurs at these interfaces resulting in low friction. Such low friction between the mold and the casting material has several advantages. First, it enables the utilization of a drier mix, such that the concrete dries faster, thereby greatly speeding up the casting process. Further, with a drier mix, the problems of slump and sagging are minimized. The low frictional contact also minimizes frictional tearing with the vertical motion of the funnel mold, resulting in an exceptionally smooth surface and minimal cracking. The sonic energy imparted to the casting material itself elastically vibrates this material, and by virtue of such vibration a superior end product is produced. Such sonic vibration of the mix first compacts and unifies the material and increases the wetting action so as to increase the strength of the concrete formed. Also, the sonic energy imparted to the material converts into heat. This heat is uniformly distributed throughout the material, making for uniform curing without causing locked-up stresses which might tend to reduce strength and cause cracking at subsequent times. This heating also speeds up the setting of the concrete.

Depending upon the structure of the slip-form member, it may be desirable to set the frequency or the location of the oscillator so as to generate a lateral wave component therealong or a longitudinal wave pattern to provide a shear wave coupling to the cement thereadjacent.

Referring now to FIG. 2, a second embodiment of the device of the invention useful in the slip-forming of concrete in making highway slabs is illustrated. Slip-form paving machine is pulled by tractor 122 to lay down a concrete slab 125. The concrete aggregate is dumped from chute 132 into hopper 135. Mounted on apron 136 of the hopper is resonant bar 137 which is resonantly excited by orbiting-mass oscillator 110. Orbiting-mass oscillator 110 may be similar in configuration to the oscillator utilized in conjunction with the embodiment of FIG. 1, i.e. it may be a. gear-driven device as described in connection with aforementioned Patent No. 3,299,722. Oscillater 110 is driven by engine 140.

Referring now to FIG. 3, it can be seen that resonant bar 137 is mounted on mounts 142 .and 143, so that the nodes of standing waves 148 are separated some short distance from these mounting points. Thus, fairly highimpedance sonic energy is delivered to apron 136, making the apron an integral portion of the resonant vibrating system. The resonant bar 137 is utilized to provide higher Q, thus aifording higher efiiciency of the sonic vibrating system. However, if so desired, sonic oscillator 110 may be mounted directly on the apron, utilizing only the apron and surrounding members to form the resonant vibrating system. As in the other embodiment, orbitingmass oscillator 110 adjusts its frequency and phase with changes in the load to maintain optimum resonant operation at all times. This type of slip-forming has the same inherent advantages as described in connection with the embodiment of FIG. 1, both speeding up the operation and resulting in a superior end product.

The devices of this invention thus provide sonic means for enhancing the slip-forming of concrete. The adhesion of such material to the flow defining members is minimized. In addition, the sonic action improves the structure of the material and facilitates the forming process.

While the devices of this invention have been described and illustrated in detail, it is to be clearly understood that this is by way of illustration and example only, the spirit and scope of this invention being limited only by the terms of the following claims.

I claim:

1. In a device for the slip-forming of concrete from concrete aggregate:

a mold member having an upper open end for receiving said concrete aggregate and a lower open end for exiting the concrete as it sets;

means for moving said mold to etfect the exiting of the formed concrete therefrom; and

an orbiting-mass sonic oscillator,

means for connecting said oscillator to said mold to resonantly vibrate said mold, said oscillator being adapted to automatically adjust its frequency to maintain resonant vibration of said mold with changes in the impedance characteristics of said concrete as it sets,

whereby said vibration lessens the friction between the mold and the concrete and improves the characteristics of the concrete.

2. The device as recited in claim 1 wherein said mold and said means for moving said mold comprises a machine for laying flat concrete slabs.

3. The device as recited in claim 1 wherein said mold and said means for moving said mold comprises a device for forming concrete columns.

4. The device as recited in claim 1 wherein said means for connecting said oscillator to said mold comprises a high-Q resonant bar attached to said mold, said oscillator being attached to said bar.

References Cited J. SPENCER OVERHOLSER, Primary Examiner ROBERT D. BALDWIN, Assistant Examiner US. Cl. X.R. 264-70 

